[MS ABI] Never reference dllimport'd vtables

Referencing a dllimported vtable is impossible in a constexpr
constructor.  It would be friendlier to C++ programmers if we
synthesized a copy of the vftable which referenced imported virtual
functions.  This would let us initialize the object in a way which
preserves both the intent to import functionality from another DLL while
also making constexpr work.

Differential Revision: http://reviews.llvm.org/D17061

llvm-svn: 260388

2 files changed, 4 insertions, 2 deletions

diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index 0634319cbd1..930cf00d9e3 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -2599,7 +2599,10 @@ void MicrosoftMangleContextImpl::mangleCXXVFTable(
   // NOTE: <cvr-qualifiers> here is always 'B' (const). <storage-class>
   // is always '6' for vftables.
   MicrosoftCXXNameMangler Mangler(*this, Out);
-  Mangler.getStream() << "\01??_7";
+  if (Derived->hasAttr<DLLImportAttr>())
+    Mangler.getStream() << "\01??_S";
+  else
+    Mangler.getStream() << "\01??_7";
   Mangler.mangleName(Derived);
   Mangler.getStream() << "6B"; // '6' for vftable, 'B' for const.
   for (const CXXRecordDecl *RD : BasePath)
diff --git a/clang/lib/AST/VTableBuilder.cpp b/clang/lib/AST/VTableBuilder.cpp
index bae018652f9..b728b279182 100644
--- a/clang/lib/AST/VTableBuilder.cpp
+++ b/clang/lib/AST/VTableBuilder.cpp
@@ -2548,7 +2548,6 @@ public:
     // Only include the RTTI component if we know that we will provide a
     // definition of the vftable.
     HasRTTIComponent = Context.getLangOpts().RTTIData &&
-                       !MostDerivedClass->hasAttr<DLLImportAttr>() &&
                        MostDerivedClass->getTemplateSpecializationKind() !=
                            TSK_ExplicitInstantiationDeclaration;